This invention relates in general to a system for powering anti-lock brakes on tractor trailers which avoids the necessity of providing additional electric lines between the tractor and trailer and further avoids the necessity of providing a separate power source on the trailer for anti-lock brakes.
In response to a directive in the Truck and Bus Safety Reform Act of 1988, the National Highway Traffic Safety Administration (NHTSA) issued a report on heavy truck and trailer brakes. "NHTSA officials are very encouraged from what they've learned so far in their 200-tractor, two year anti-lock brake tests which will conclude at the end of this month" (Heavy Duty Trucking, June 1991, pg. 10). "It's a virtual certainty that Congress and NHTSA will require anti-lock. It's just a matter of time. Anti-lock will come first on tractors, later on trailers--perhaps by 1996" (Heavy Duty Trucking, November 1991, pg. 67).
One major difference between tractor anti-lock brakes and trailer anti-lock brakes is that tractor anti-lock brakes are powered continuously from the tractor electrical system, whereas trailer anti-lock brakes must derive their power from the trailer stop light circuit as required under current Federal Motor Vehicle Safety Standard (FMVSS) No. 121. This arrangement is less than ideal since power is supplied to the trailer anti-lock system only when brakes are applied. With continuous power as provided in the present invention, the trailer's ECU (Electronic Control Unit) of the anti-lock system can perform periodic self-checks, which enhances the system's reliability. Both vehicle and anti-lock manufacturers, as well as NHTSA and the fleets want to find out about anti-lock performance and reliability when powering the trailer anti-lock systems in ways other than the intermittent trailer stop light circuit.
A second portion of the NHTSA field test--trailer anti-lock--is now being conducted and is scheduled to run until 1993, when most trailers will have run two years.
Four different systems of powering anti-lock brakes on trailers will be tested and are as follows:
1) The standard seven-pin cord and plug configuration between tractor and trailer that is currently in widespread use will provide power from the stop light circuit only when brakes are applied. With this system, any tractor remains interchangeable with any trailer;
2) A European-style ISO connector will provide power to the anti-lock brake system in addition to the standard seven-pin cord and plug configuration. This requires both tractor and trailer to be wired with two connectors, the second one powering trailer anti-lock brakes;
3) A "halo" connector will provide power to the anti-lock brake system. This is a seven-pin modified configuration to include an additional eight circuits. Trailers using the additional eight circuits will need nose boxes of special design to mate with this connector;
4) Battery power on the trailer will provide power to the anti-lock brake system. An inboard battery system will provide constant voltage to anti-lock ECU's. The battery will be charged through the seventh unused pin (which is already used by many fleets to power trailer accessories such as interior lights) in the trailer cord.
The present invention provides a system for powering anti-lock brake systems on tractor trailers by use of the standard existing seven way cord and plug configuration used between a tractor and a trailer without modifying the seven way cord and plug configuration and provides continuous electrical power to the anti-lock brake system.
Some examples of prior art anti-lock brake powering systems are set forth in patents briefly described below:
U.S. Pat. No. 5,039,173 issued to Emig et al. discloses a system providing a separate battery located on the trailer which in combination with the tractor power source, powers the anti-lock brake system and the electronic control unit of the system. This system requires an additional battery which has encountered charging difficulties in the field, requires periodic maintenance, and the installation of such a system is expensive.
U.S. Pat. No. 5,085,489 issued to Emig et al. discloses a system which powers the electronic control unit of the anti-lock brake system from wheel sensors and solenoid valves and from the brake light circuit. This system supplies only partial power to the electronic control unit and no power to the solenoid valves of the anti-lock brake system. The wheel sensors are susceptible to mechanical failure and the system does not supply power unless the wheels of the trailer are moving above a set speed.
Whatever the precise merits, features and advantages of the aforecited references, none fulfills the purpose of the present invention.
The present invention allows the continued use of the standard existing seven way cord and plug configuration presently used on tractor and trailer systems and provides continuous electrical power to the anti-lock brake system of the trailer. Since there is continuous electrical power supplied in the invention, no warm up or self-diagnostics time is necessary before the anti-lock brake system is functional and thus the present invention enhances braking response time. In addition where additional double or triple trailers are used, the present invention maintains a more stable power supply that helps to overcome voltage drop problems between the multiple trailer units.
A further object of the present invention is to eliminate the necessity for an additional power cord from the tractor to the trailer or additional batteries on the trailer to power the anti-lock brake system. By making use of the present existing standard seven way cord and plug configuration between the tractor and trailer, no additional power cord is necessary and no additional power source on the trailer is necessary to power the anti-lock brake system.
Still another object of the present invention is to permit diagnostics to operate continuously in the anti-lock brake system and not just when the brakes are applied as is the case in some of the prior art. In addition, minimal expense is incurred in adapting present tractor trailer systems to the present invention.
Yet another object of the present invention is to permit tractors to be used interchangeably with trailers equipped with either a conventional brake system or an anti-lock brake system.
Further the present invention enhances operation and safety of tractor trailer vehicles by providing continuous electrical power to the anti-lock brake systems.